diff --git a/completions/bun.bash b/completions/bun.bash
index 2188be22e344..46fccd821969 100644
--- a/completions/bun.bash
+++ b/completions/bun.bash
@@ -170,6 +170,14 @@ _bun_completions() {
             _read_scripts_in_package_json;
             _subcommand_comp_reply "${cur_word}" "${SUBCOMMANDS}";
 
+            # `bun <file> <args...>` — the first word isn't a recognised
+            # subcommand, so treat it as a script path and complete
+            # positional args after the script with files. Without this
+            # branch, `bun myscript.ts foo<TAB>` does nothing.
+            (( COMP_CWORD >= 2 )) && {
+                COMPREPLY+=( $(compgen -f -- "${cur_word}") );
+            }
+
             # determine if completion should be continued
             # when the current word is an empty string
             # the previous word is not part of the allowed completion
diff --git a/completions/bun.zsh b/completions/bun.zsh
index 34940fef1103..d4c4b2879cb9 100644
--- a/completions/bun.zsh
+++ b/completions/bun.zsh
@@ -928,6 +928,13 @@ _bun() {
                 ;;
             esac
 
+            ;;
+        *)
+            # `bun <file> ...` — the first word isn't a known subcommand,
+            # so bun treats it as a script path. Complete positional args
+            # after the script with files, mirroring what `bun run` does.
+            _files
+
             ;;
         esac
 
diff --git a/test/cli/completions.test.ts b/test/cli/completions.test.ts
new file mode 100644
index 000000000000..9c8332beb8ca
--- /dev/null
+++ b/test/cli/completions.test.ts
@@ -0,0 +1,265 @@
+import { describe, expect, test } from "bun:test";
+import { bunEnv, isWindows, tempDir } from "harness";
+import path from "node:path";
+
+// Repo-relative paths to the completion scripts being exercised.
+const BASH_COMPLETION = path.join(import.meta.dir, "..", "..", "completions", "bun.bash");
+const ZSH_COMPLETION = path.join(import.meta.dir, "..", "..", "completions", "bun.zsh");
+
+// Single-quote a string for embedding inside a shell single-quoted string.
+const sq = (s: string) => `'${s.replace(/'/g, `'\\''`)}'`;
+
+// Spawn bash, source the completion script, drive `_bun_completions` with a
+// simulated command line, and return the resulting COMPREPLY list.
+async function bashComplete(cwd: string, words: string[], cwordIndex: number): Promise<string[]> {
+  const compWords = words.map(sq).join(" ");
+  const script = [
+    "set +e",
+    "shopt -s extglob",
+    `source ${sq(BASH_COMPLETION)}`,
+    `COMP_WORDS=(${compWords})`,
+    `COMP_CWORD=${cwordIndex}`,
+    `COMP_LINE=${sq(words.join(" "))}`,
+    `COMP_POINT=\${#COMP_LINE}`,
+    "COMPREPLY=()",
+    "_bun_completions",
+    // Emit each match on its own line prefixed with a sentinel so we can
+    // distinguish it from stray diagnostic output.
+    `for m in "\${COMPREPLY[@]}"; do printf 'COMP:%s\\n' "$m"; done`,
+  ].join("\n");
+  await using proc = Bun.spawn({
+    cmd: ["bash", "-c", script],
+    env: bunEnv,
+    cwd,
+    stdin: "ignore",
+    stdout: "pipe",
+    stderr: "pipe",
+  });
+  const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
+  if (exitCode !== 0) {
+    throw new Error(`bash driver exited with code ${exitCode}\nstdout:\n${stdout}\nstderr:\n${stderr}`);
+  }
+  return stdout
+    .split("\n")
+    .filter(l => l.startsWith("COMP:"))
+    .map(l => l.slice("COMP:".length));
+}
+
+// Is zsh available? Only relevant for the zsh-specific coverage below;
+// if unavailable the zsh tests silently pass (bash covers the same logic).
+async function zshAvailable(): Promise<boolean> {
+  try {
+    await using proc = Bun.spawn({
+      cmd: ["zsh", "-c", "exit 0"],
+      env: bunEnv,
+      stdout: "ignore",
+      stderr: "ignore",
+    });
+    return (await proc.exited) === 0;
+  } catch {
+    return false;
+  }
+}
+
+// Drive zsh tab completion by spawning an embedded zsh via zpty, sending a
+// command line followed by a literal TAB, and returning the terminal buffer
+// up to the point where `expected` appears (success) or a BEL byte appears
+// (zsh's "no match" signal — also a terminal state, just a failing one).
+// This is poll-until-seen, not sleep-based, so it's fast in the common case
+// and robust under CI load.
+async function zshCompleteLine(cwd: string, line: string, expected: string): Promise<string> {
+  // Outer zsh uses zpty to drive an inner interactive zsh, feeds setup
+  // commands (each emitting a marker so we can synchronise on it), then
+  // writes `<line><TAB>` and polls the pty buffer until `expected` or a
+  // bell arrives.
+  const script = [
+    "emulate -L zsh",
+    // Needed for `[0-9;]#m` (zsh "zero or more") in the ANSI-stripping glob.
+    "setopt extendedglob",
+    "zmodload zsh/zpty",
+    // wait_for <needle> [timeout]: read zpty S until <needle> appears in
+    // the accumulated buffer, with a poll interval. `zpty -r -t` on a
+    // non-blocking pty returns immediately when there's no data, so we
+    // sleep between polls to avoid pegging a core.
+    `wait_for() {
+        local needle="$1" timeout=\${2:-10} buf='' chunk
+        local start=$SECONDS
+        while (( SECONDS - start < timeout )); do
+            if zpty -r -t S chunk 2>/dev/null; then
+                buf+="$chunk"
+                [[ "$buf" == *$needle* ]] && { printf '%s' "$buf"; return 0; }
+            else
+                sleep 0.02
+            fi
+        done
+        printf '%s' "$buf"
+        return 1
+    }`,
+    "zpty -b S zsh -i -f",
+    // Set up the inner shell. `compinit -D` skips writing `~/.zcompdump`
+    // so tests running concurrently never race on that file.
+    "zpty -w S 'PS1=\"\"; autoload -Uz compinit && compinit -D; echo __INIT__'",
+    "wait_for __INIT__ >/dev/null || { echo >&2 'inner zsh setup timed out'; exit 1; }",
+    // `zpty -w` takes the argument verbatim as what to type at the inner
+    // shell's prompt. We wrap the argument in single quotes (escaping
+    // inner single quotes via the standard `'\''` dance) and sq() does
+    // that for us. The inner `cd` and `source` commands then quote the
+    // path values themselves.
+    `zpty -w S ${sq("cd " + sq(cwd) + "; source " + sq(ZSH_COMPLETION) + "; echo __LOADED__")}`,
+    "wait_for __LOADED__ >/dev/null || { echo >&2 'completion load timed out'; exit 1; }",
+    "zpty -w S 'bindkey \"^I\" expand-or-complete; setopt no_always_last_prompt no_list_beep; echo __BOUND__'",
+    "wait_for __BOUND__ >/dev/null || { echo >&2 'bindkey timed out'; exit 1; }",
+    // Drain anything remaining from setup.
+    "while zpty -r -t S junk 2>/dev/null; do :; done",
+    // Literal tab triggers `expand-or-complete`. It either moves the
+    // buffer past `<line>` (success) or rings the bell (BEL = 0x07) when
+    // there's no match.
+    `zpty -n -w S ${sq(line + "\t")}`,
+    // Poll until either the expected substring or a BEL appears — that's
+    // our "I'm done" signal, replacing a fixed sleep. 4s upper bound
+    // keeps us well under bun:test's default 5s test timeout even under
+    // CI load; the common case is <1s.
+    //
+    // We strip ANSI escape sequences from the accumulated buffer BEFORE
+    // matching the needle because zsh's list-colors can insert colour
+    // codes between individual characters of the completed token (e.g.
+    // `foo\x1b[32m\x1b[39m-`), which would prevent a naive substring
+    // check from matching.
+    `local needle=${sq(expected)}`,
+    `local out='' visible chunk start=$SECONDS`,
+    "while (( SECONDS - start < 4 )); do",
+    "    if zpty -r -t S chunk 2>/dev/null; then",
+    '        out+="$chunk"',
+    `        visible=\${out//\$'\\x1b'\\[[0-9;]#m/}`,
+    // $'\a' is the BEL byte (0x07). Zsh rings this on a failed completion.
+    `        [[ "$visible" == *$'\\a'* ]] && break`,
+    '        [[ "$visible" == *$needle* ]] && break',
+    "    else",
+    "        sleep 0.02",
+    "    fi",
+    "done",
+    "zpty -d S",
+    `printf '%s' "$visible"`,
+  ].join("\n");
+  await using proc = Bun.spawn({
+    cmd: ["zsh", "-c", script],
+    env: bunEnv,
+    cwd,
+    stdin: "ignore",
+    stdout: "pipe",
+    stderr: "pipe",
+  });
+  const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
+  if (exitCode !== 0) {
+    throw new Error(`zsh driver exited with code ${exitCode}\nstdout:\n${stdout}\nstderr:\n${stderr}`);
+  }
+  return stdout;
+}
+
+describe.skipIf(isWindows)("shell completions", () => {
+  // Every test here spawns its own short-lived subprocess into its own
+  // tempDir — no shared state, so we prefer concurrent per CLAUDE.md.
+  describe.concurrent("bash (completions/bun.bash)", () => {
+    // Regression for #30386: `bun myscript.ts foo<TAB>` did nothing. When
+    // the first word after `bun` isn't a recognised subcommand, the
+    // `case ${COMP_WORDS[1]} in ... *)` fallback in completions/bun.bash
+    // never called into file completion, so positions 2+ got no files.
+    test("completes files for `bun <script> <arg><TAB>`", async () => {
+      using dir = tempDir("bun-complete-bash-30386", {
+        "myscript.ts": "",
+        "foo-file.txt": "",
+        "foo-bar.txt": "",
+        "bar.txt": "",
+      });
+      const matches = await bashComplete(String(dir), ["bun", "myscript.ts", "foo"], 2);
+      expect(matches.sort()).toEqual(["foo-bar.txt", "foo-file.txt"]);
+    });
+
+    // Same shape, multiple positional args deep: the cwordIndex is 3 here
+    // (`foo` at position 3), the first arg is still a script.
+    test("completes files for `bun <script> <arg1> <arg2><TAB>`", async () => {
+      using dir = tempDir("bun-complete-bash-30386-deep", {
+        "myscript.ts": "",
+        "foo-file.txt": "",
+        "foo-bar.txt": "",
+      });
+      const matches = await bashComplete(String(dir), ["bun", "myscript.ts", "prev-arg", "foo"], 3);
+      expect(matches.sort()).toEqual(["foo-bar.txt", "foo-file.txt"]);
+    });
+
+    // Guards against the first-arg path breaking — typing a partial script
+    // name should still be valid input (no throw, reasonable output).
+    test("does not throw on first-arg completion", async () => {
+      using dir = tempDir("bun-complete-bash-30386-first", {
+        "myscript.ts": "",
+      });
+      const matches = await bashComplete(String(dir), ["bun", "mysc"], 1);
+      // First-arg behaviour is governed elsewhere (main_commands + scripts).
+      // The only thing we care about here is that driving the completion
+      // doesn't error out.
+      expect(Array.isArray(matches)).toBe(true);
+    });
+  });
+
+  describe.concurrent("zsh (completions/bun.zsh)", () => {
+    // The bug in #30386 was reported against zsh on macOS; the fix mirrors
+    // the bash one by adding a `*)` default branch to the `case $line[1]`
+    // dispatch. The observable fix: typing `bun myscript.ts foo<TAB>`
+    // now auto-completes to `foo-` (the common prefix of the matching
+    // files). Before the fix, the buffer stays at `foo` and zsh rings
+    // the bell (BEL byte in the pty output).
+    test("completes files for `bun <script> <arg><TAB>`", async () => {
+      if (!(await zshAvailable())) return;
+      using dir = tempDir("bun-complete-zsh-30386", {
+        "myscript.ts": "",
+        "foo-file.txt": "",
+        "foo-bar.txt": "",
+      });
+      const out = await zshCompleteLine(String(dir), "bun myscript.ts foo", "bun myscript.ts foo-");
+      expect(out).toContain("bun myscript.ts foo-");
+    });
+
+    // Regression guard: `bun run <script> <arg><TAB>` already worked
+    // before this fix (via the `run)` branch's `other)` state). Assert it
+    // still does after the new `*)` branch was added.
+    test("completes files for `bun run <script> <arg><TAB>`", async () => {
+      if (!(await zshAvailable())) return;
+      using dir = tempDir("bun-complete-zsh-30386-run", {
+        "myscript.ts": "",
+        "foo-file.txt": "",
+        "foo-bar.txt": "",
+      });
+      const out = await zshCompleteLine(String(dir), "bun run myscript.ts foo", "bun run myscript.ts foo-");
+      expect(out).toContain("bun run myscript.ts foo-");
+    });
+  });
+
+  describe.concurrent("syntax", () => {
+    // Catch-all: every shell completion script must parse cleanly.
+    // Prevents future edits from breaking the scripts at source-load time.
+    test("bun.bash parses", async () => {
+      await using proc = Bun.spawn({
+        cmd: ["bash", "-n", BASH_COMPLETION],
+        env: bunEnv,
+        stdout: "pipe",
+        stderr: "pipe",
+      });
+      const [stderr, exitCode] = await Promise.all([proc.stderr.text(), proc.exited]);
+      expect(stderr).toBe("");
+      expect(exitCode).toBe(0);
+    });
+
+    test("bun.zsh parses", async () => {
+      if (!(await zshAvailable())) return;
+      await using proc = Bun.spawn({
+        cmd: ["zsh", "-n", ZSH_COMPLETION],
+        env: bunEnv,
+        stdout: "pipe",
+        stderr: "pipe",
+      });
+      const [stderr, exitCode] = await Promise.all([proc.stderr.text(), proc.exited]);
+      expect(stderr).toBe("");
+      expect(exitCode).toBe(0);
+    });
+  });
+});